1. Field of the Invention
The present invention relates to a spark plug for use in an internal combustion engine of an automobile, a cogeneration apparatus, a gas feed pump, etc., and to a method of manufacturing the spark plug.
2. Description of Related Art
Generally, a spark plug for use in an internal combustion engine includes a center electrode, an insulator disposed around the outer periphery of the center electrode, a mounting bracket disposed around the outer periphery of the insulator, and a ground electrode disposed so as to extend from the mounting bracket and form a spark discharge gap with the center electrode. It is known to provide such a spark plug with a highly durable noble-metal chip at the spark discharge gap thereof. For example, refer to Japanese Patent Application Laid-open No. 2011-34826.
Incidentally, since the joining between the noble-metal chip and the center electrode or ground electrode as a base material electrode is performed by welding, a weld portion is formed therebetween. Accordingly, to achieve high durability thanks to the noble-metal chip, the reliability between the noble-metal chip and the base material electrode through the weld portion has to be sufficiently high.